God save us from conspiracy theorists, were Senator Joseph Lieberman to be elected US president in 2004. Things are quite bad enough as they stand, without a Jewish head of state in America. Fortunately, it looks as though George Bush will win, whoever his opponent is.

For the past 40 years, the common explanation for US partiality towards Israel has been the power of the Jewish lobby. It is an explanation that, broadly, has united leftwingers and rightwingers. Why has the United States been so supine in the face of Israeli intransigence, and so uncaring in its attitude towards the plight of the Palestinians? Above all, why has it behaved in this way, when a more balanced approach might have served its long-term interests far better? The Jewish lobby, that's why.

The lobby explanation has been outlined with great clarity by Mark Weber, who is director of the American Institute for Historical Review. In a long article, Weber brought together the comments and analyses of various Jewish academics, such as Benjamin Ginsberg of Johns Hopkins University, and writers such as Seymour Lipset and Earl Raab. Ginsberg, for example, wrote in his book, The Fatal Embrace: "Since the 1960s, Jews have come to wield considerable influence in American economic, cultural, intellectual and political life ... close to half its billionaires are Jews. The chief executive officers of the three major television networks and the four largest film studios are Jews, as are the owners of the nation's largest newspaper chain and the single most influential newspaper, the New York Times."

Lipset and Raab gave further figures, noting (according to Weber) that Jews constituted "50% of the top 200 intellectuals ... 20% of professors at the leading universities ... 40% of partners in the leading law firms in New York and Washington." Etcetera, schmetcetera. You get the idea.

Weber, as one of America's leading Holocaust deniers, is perfectly happy, but I can see that old Ginsberg has terrific problems with the fact that Jews have cropped up in almost all of the major 19th and 20th-century political movements - many of them completely contradictory. They are cited as leading forces in liberalism, neo-conservatism, socialism, bolshevism and market capitalism. The only two movements that Jews don't seem to have led are fascism and Islamic fundamentalism. Still, they were the guys behind Reagan, the guys behind Clinton - either ever mutating, ever powerful (if you're a conspiracist), or ever disagreeing with each other if you're not.

The other difficulty for non-conspiracists is that there just aren't that many Jews in America. Six million is the latest figure (3.9% of the population in Florida, and 128,000 out of 21 million in Dubya's Texas), and probably declining. The Muslim population is about 3.5 million and growing.

The electoral-lobby thing doesn't work any more. Enter, lowered from the gods, another story. This is that Israel is currently being sustained in its Sharonite nastiness by a new lobby - the Christian right. This may seem strange in view of the ol'-time anti-semitism of many people, such as preacher/politician Pat Robertson, but the transmission is supposed to work like this.

1. Lots of these Christian folks are dispensationalists, who believe that we are living in the sixth dispensation, and the seventh (shortly upon us) will be a millennium-long earthly reign, based in Israel. (Warning note: We have to have a rapture first, and their idea of rapture is different from that of most Guardian readers.)

2. For this to happen, all the Jews have to go to Israel and then convert to Christianity or die.

3. So they want the Jews to get the whole of Palestine, and quickly.

4. George Bush is a born-again Christian, as are many of his cronies, so either 5. he believes all this stuff and bases his foreign policy on it, or 6. he bends to the dispensationalists because he needs their votes.

I have read this account in several newspapers and, last Sunday, heard it delivered, uninterrogated, on Radio 4. And it just occurs to me that there might be other, less obviously ridiculous explanations for American policy on Israel over the years. They could include the legacy of the cold war - when the USSR sided with the Arab nations; a respect for Israeli democracy (flawed though it might be); a penchant for the underdog (now fading); and - above all - an identification with a pioneering people who made a life in a new land, and displaced another people in order to do it.

I do accept, however, that this lacks the narrative drive of the other versions, and await the moment when we discover that Joe Lieberman is also the Grand Master of the Priory of Sion, who has bought his election with the fabulous Templar treasure, dug up at Rennes-le-Cateau. That's what I call a story.